{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,5]],"date-time":"2026-04-05T19:48:51Z","timestamp":1775418531544,"version":"3.50.1"},"reference-count":19,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2015,7,17]],"date-time":"2015-07-17T00:00:00Z","timestamp":1437091200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Characterizing a surface defect is very crucial in non-destructive testing (NDT). We employ an electromagnetic acoustic transducer (EMAT) to detect the surface defect of a nonmagnetic material. An appropriate feature that can avoid the interference of the human factor is vital for evaluating the crack quantitatively. Moreover, it can also reduce the influence of other factors, such as the lift-off, during the testing. In this paper, we conduct experiments at various depths of surface cracks in an aluminum plate, and a new feature, lift-off slope (LOS), is put forward for the theoretical and experimental analyses of the lift-off effect on the receiving signals. Besides, by changing the lift-off between the receiving probe and the sample for testing, a new method is adopted to evaluate surface defects with the EMAT. Compared with other features, the theoretical and experimental results show that the feature lift-off slope has many advantages prior to the other features for evaluating the surface defect with the EMAT. This can reduce the lift-off effect of one probe. Meanwhile, it is not essential to measure the signal without defects.<\/jats:p>","DOI":"10.3390\/s150717420","type":"journal-article","created":{"date-parts":[[2015,7,17]],"date-time":"2015-07-17T11:18:48Z","timestamp":1437131928000},"page":"17420-17432","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["A New Method to Evaluate Surface Defects with  an Electromagnetic Acoustic Transducer"],"prefix":"10.3390","volume":"15","author":[{"given":"Kang","family":"Zhang","sequence":"first","affiliation":[{"name":"School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pengxing","family":"Yi","sequence":"additional","affiliation":[{"name":"School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yahui","family":"Li","sequence":"additional","affiliation":[{"name":"School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bing","family":"Hui","sequence":"additional","affiliation":[{"name":"School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4332-071X","authenticated-orcid":false,"given":"Xuming","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Life Science & Technology, Huazhong University of Science & Technology,  Wuhan 430074, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2015,7,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.ndteint.2014.03.007","article-title":"A new electromagnetic acoustic transducer (EMAT) design for operation on rail","volume":"65","author":"Petcher","year":"2014","journal-title":"NDT&E Int."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"675","DOI":"10.1016\/j.ultras.2011.01.009","article-title":"Improving the signal amplitude of meandering coil EMATs by using ribbon soft magnetic flux concentrators (MFC)","volume":"51","author":"Dhayalan","year":"2011","journal-title":"Ultrasonics"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1016\/j.ndteint.2012.06.004","article-title":"The impact of magnetostriction on the transduction of normal bias field EMATs","volume":"51","author":"Ribichini","year":"2012","journal-title":"NDT&E Int."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.ndteint.2011.08.007","article-title":"Experimental and numerical evaluation of electromagnetic acoustic transducer performance on steel materials","volume":"45","author":"Ribichini","year":"2012","journal-title":"NDT&E Int."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e1401","DOI":"10.1016\/j.ultras.2006.05.169","article-title":"Lift-off compensation for improved accuracy in ultrasonic lamb wave velocity measurements using electromagnetic acoustic transducers (EMATs)","volume":"44","author":"Morrison","year":"2006","journal-title":"Ultrasonics"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"700","DOI":"10.1016\/j.cemconcomp.2007.05.001","article-title":"Repair evaluation of concrete cracks using surface and through-transmission wave measurements","volume":"29","author":"Aggelis","year":"2007","journal-title":"Cem. 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